Precision Measurement of the Mass and Lifetime of the Ξ0b Baryon

Using a proton-proton collision data sample corresponding to an integrated luminosity of 3 fb^−1 collected by LHCb at center-of-mass energies of 7 and 8 TeV, about 3800 Ξ0b → Ξ+c π−, Ξ+c → p K− π+ signal decays are reconstructed. From this sample, the first measurement of the Ξ0b baryon lifetime is made, relative to that of the Λ0b baryon. The mass differences M(Ξ0b) − M(Λ0b) and M(Ξ+c) − M(Λ+c) are also measured with precision more than 4 times better than the current world averages. The resulting values are τ(Ξ0b)/τ(Λ0b) = 1.006 ± 0.018 ± 0.010, M(Ξ0b) − M(Λ0b) = 172.44 ± 0.39 ± 0.17 MeV/c2, M(Ξ+c) − M(Λ+c) = 181.51 ± 0.14 ± 0.10 MeV/c2, where the first uncertainty is statistical and the second is systematic. The relative rate of Ξ0b to Λ0b baryon production is measured to be f(Ξ0b)/f(Λ0b) B(Ξ0b → Ξ+c π−)/B(Λ0b → Λ+c π−) B(Ξ+c → p K− π+)/B(Λ+c → p K− π+) = (1.88 ± 0.04 ± 0.03)×10^−2, where the first factor is the ratio of fragmentation fractions, b → Ξ0b relative to b → Λ0b. Relative production rates as functions of transverse momentum and pseudorapidity are also presented.